Mojo: NULL -> nullptr in mojo/public/cpp/bindings and also for the bindings generator.

mojo/public/cpp/bindings/lib/message_header_validator.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MOJO_PUBLIC_CPP_BINDINGS_LIB_MESSAGE_HEADER_VALIDATOR_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_LIB_MESSAGE_HEADER_VALIDATOR_H_
 
 #include "mojo/public/cpp/bindings/message.h"
 #include "mojo/public/cpp/bindings/message_filter.h"
 
 namespace mojo {
 namespace internal {
 
 class MessageHeaderValidator : public MessageFilter {
  public:
-  explicit MessageHeaderValidator(MessageReceiver* sink = NULL);
+  explicit MessageHeaderValidator(MessageReceiver* sink = nullptr);
 
   virtual bool Accept(Message* message) override;
 };
 
 }  // namespace internal
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_LIB_MESSAGE_HEADER_VALIDATOR_H_